Cognizant Frontend Software Developer Interview Questions and Answers

Q1. Explain Virtual DOM, Key Features of React, Hooks in React, create a todo app in react
Ans. 
Virtual DOM is a lightweight copy of the actual DOM, React key features include component-based architecture, declarative syntax, and virtual DOM, React Hooks are functions that let you use state and other React features without writing a class.
• Virtual DOM is a lightweight copy of the actual DOM that React uses to improve performance by updating only the necessary parts of the DOM.

• Key features of React include componen...read more
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Q2. Javascript Questions- Closures,promises,Async/await,setTimeOut, write acode to reverse a string
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Q1. Self Introduction, some situation based questions
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Q2. Basic HR regular questions
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Q1. MCQ questioons were there based on angular framework
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Q2. Services mcq were there
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Q1. What is Dependecy Injection
Ans. 
Dependency Injection is a design pattern in which a class receives its dependencies from external sources rather than creating them itself.
• Allows for easier testing by injecting mock dependencies

• Promotes reusability and modularity by decoupling components

• Reduces code duplication by centralizing dependency creation

• Example: Angular uses Dependency Injection to provide services to components
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Q2. What is routing
Ans. 
Routing is the process of navigating between different pages or views in a web application.
• Routing allows users to move between different parts of a web application without reloading the entire page

• It is implemented using a router module in Angular, which maps URLs to components

• Routes can have parameters that can be passed to components for dynamic content

• Routing can be used to create single-page applications (SPAs) wh
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Ages, odd numbers, number series, work and time, calendars.

Youth in politics and artificial intelligence.

Quantitative aptitude, logical apptiude,

Q1. Data structure and algorithms
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Q2. Programming concepts
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Q1. Basic angular questions
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Q2. Scenario based questions
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Q3. NgRx related questions
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Q1. Why do we use Debugger in Javascript?
Ans. 
Debugger in JavaScript is used for pausing the execution of code to inspect variables, check the flow of the program, and debug errors.
• Debugger helps in identifying and fixing bugs in the code.

• It allows developers to step through code line by line to understand the flow of execution.

• Developers can inspect variables and their values at different points in the code.

• By setting breakpoints, developers can pause the code at...read more
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Q1. Frontend developer
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Html, CSS, bootstrap, JavaScript, react.js

Q1. How directives are different from component
Ans. 
Directives are used to add behavior to existing DOM elements, while components are used to create new custom elements.
• Directives are used to manipulate the behavior of existing DOM elements, such as changing their appearance or adding event listeners.

• Components are used to create custom elements with their own templates, styles, and behavior.

• Directives can be structural (like ngIf and ngFor) or attribute-based (like ng...read more
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Q2. What is hoisting
Ans. 
Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.
• Variable and function declarations are hoisted to the top of their scope, regardless of where they are declared in the code.

• Only the declarations are hoisted, not the initializations.

• Function declarations are hoisted before variable declarations.
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Q1. Explain design patterns.
Ans. 
Design patterns are reusable solutions to common problems in software design.
• Design patterns help in creating maintainable, scalable, and efficient code.

• They provide a common language for developers to communicate about solutions to recurring problems.

• Examples of design patterns include Singleton, Factory, Observer, and Strategy patterns.
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Q2. Explain subject. what is replay subject
Ans. 
ReplaySubject is a type of Subject in RxJS that records multiple values and replays them to new subscribers.
• ReplaySubject is a type of Subject in RxJS

• It records multiple values and replays them to new subscribers

• It has a buffer size that determines how many values to replay
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Q1. Salary discussion
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